Heart Failure or Congestive Heart Failure affects approximately five million Americans. CHF is characterized by the Medline Encyclopedia as a life-threatening condition in which the heart can no longer pump enough blood to meet the demands of the body. Heart failure is almost always a chronic, long-term condition, although it can sometimes develop suddenly. This condition may affect the right side, the left side, or both sides of the heart. As the heart's pumping action is lost, blood may back up into other areas of the body, including:                the liver;        the gastrointestinal tract and the extremities (right-sided heart failure); and        the lungs (left-sided heart failure).        
With heart failure, many organs do not receive enough oxygen and nutrients. This damages the organs and reduces their ability to function properly. Most areas of the body may be affected when both sides of the heart fail.
A common cause of heart failure is hypertension (i.e., high blood pressure). Another common cause of heart failure is coronary artery disease (e.g., a heart attack). Other structural or functional causes of heart failure include:
Valvular heart disease;
Congenital heart disease;
Dilated cardiomyopathy;
Lung disease; and
Heart tumor.
Heart failure is more common with advancing age. Risk factors for developing heart failure include being overweight, having diabetes, smoking cigarettes, abusing alcohol, or using cocaine.
There are devices that may be useful in diagnosing a patient's heart failure condition. For example, imaging tools may be used. In this regard, echocardiography is commonly used to support a clinical diagnosis of heart failure. This analysis uses ultrasound to determine a stroke volume (“SV”). A stroke volume is an amount of blood in the heart that exits the ventricles with each beat. The analysis may also determine an end-diastolic volume (“EV”) or total amount of blood at the end of diastole. The analysis may also be used to determine the SV in proportion to the EV. This proportion is a value known as the ejection fraction (“EF”). In pediatrics, the shortening fraction is the preferred measure of systolic function. Normally, the EF should be between 50% and 70%. However, in systolic heart failure, the EV typically drops below 40%. Echocardiography may also be used to identify valvular heart disease and assess the state of the pericardium (i.e., the connective tissue sac surrounding the heart). Echocardiography may also aid in deciding what treatments will help the patient, such as medication, insertion of an implantable cardioverter-defibrillator or cardiac resynchronization therapy.
Chest X-rays are another frequently used tool for diagnosing CHF. In the compensated patient, this may show cardiomegaly (a visible enlargement of the heart), quantified as the cardiothoracic ratio (a proportion of the heart size to the chest). In left ventricular failure, there may be evidence of vascular redistribution (“upper lobe blood diversion” or “cephalization”), Kerley lines, cuffing of the areas around the bronchi, and interstitial edema.
An electrocardiogram (ECG/EKG) may be used to identify arrhythmias, ischemic heart disease, right and left ventricular hypertrophy, and presence of conduction delay or abnormalities (e.g. left bundle branch block). These results may be evaluated in making a diagnosis of heart failure.
Blood tests may also be used to diagnose the condition. For example, measures of electrolytes (sodium, potassium), measures of renal function, liver function tests, thyroid function tests, a complete blood count, and often C-reactive protein if an infection is possible, may be used to diagnose the patient's condition. One specific test for heart failure determines the level of B-type natriuretic peptide (BNP). An elevated level of BNP may suggest the existence of heart failure. The BNP level may differentiate heart failure as a cause of dyspnea from other conditions that may cause dyspnea. If myocardial infarction is a possibility, cardiac markers may be used in the diagnosis of heart failure.
A patient's heart failure condition may be the result of coronary artery disease. The condition may depend on the ability of the coronary arteries to provide blood to the myocardium. Thus, a coronary catheterization may also help to identify possibilities for revascularization through percutaneous coronary intervention or bypass surgery.
Different measures may be determined to assess the progress of a patient's heart failure condition. A fluid balance or calculation of fluid intake and excretion can assist in monitoring a patient's condition. Similarly, changes in body weight, which may reflect fluid shifts, can be considered.
There is no present gold standard in the diagnosis of heart failure. The Framingham criteria, which was derived from the Framingham Heart Study, the Boston criteria, the Duke criteria and the Killip classification are systems that are commonly considered in evaluating a patient for heart failure.
A functional classification of heart failure may also be considered by classes defined by the New York Heart Association Functional Classification (NYHAFC). A score according to this classification system grades the severity of symptoms, and can be used to assess the patient's responses to treatment. While it is commonly used, the NYHAFC score may not be reliably reproducible.
The classes (I-IV) of the NYHAFC system are:
Class I: no limitation is experienced in any activities; there are no symptoms from ordinary activities.
Class II: slight, mild limitation of activity; the patient is comfortable at rest or with mild exertion.
Class III: marked limitation of any activity; the patient is comfortable only at rest.
Class IV: any physical activity brings on discomfort and symptoms occur at rest.
In its 2001 guidelines, the American College of Cardiology/American Heart Association working group introduced four stages of heart failure:
Stage A: a high risk HF in the future but no structural heart disorder;
Stage B: a structural heart disorder but no symptoms at any stage;
Stage C: previous or current symptoms of heart failure in the context of an underlying structural heart problem, but managed with medical treatment;
Stage D: advanced disease requiring hospital-based support, a heart transplant or palliative care.
It will be appreciated that there is a need in the art for improved techniques and devices for addressing the conditions of heart failure.